Device for non-uniformity correction

ABSTRACT

Optical systems that provide non-uniformity correction devices that are capable of providing low radiance level sources.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 16/685,653, entitled DEVICE FOR NON-UNIFORMITY CORRECTION,filed on Nov. 15, 2019, which is a continuation of co-pending U.S.patent application Ser. No. 15/588,899, entitled DEVICE FORNON-UNIFORMITY CORRECTION, filed on May 8, 2017, which claims thebenefit of and priority to U.S. Provisional Application No. 62/339,602,entitled DEVICE FOR NON-UNIFORMITY CORRECTION, filed on May 20, 2016,the entire contents of which are incorporated herein by reference forall purposes.

BACKGROUND

These teachings relate to optical systems in which the range ofradiances for performing non-uniformity correction or radiometriccalibration of the sensor is greatly increased.

Current detector technologies, particularly those operating in theinfrared portion of the spectrum, often have significant amounts ofnon-uniformity, which cause the imagery generated by imaging andhyperspectral imaging sensors to be non-uniform in their output. Currentapproaches to the correction, or flattening, of this output imagery isaccomplished through various non-uniformity correction, more commonlyknown as NUC, methods, where images of uniform scenes at differentradiance levels are used to calculate the response of each pixel in theimagery, and then calculate an array of transformation terms to matchthe response of each pixel to a uniform average.

For example, in a two-point NUC approach, one would typically expose thesensor to two separate uniform radiance sources and then use the outputimagery to calculate an array of individual linear fits to the data.These linear fit terms would then be used to calculate a transformmatrix of gain and offset terms, which when applied to the outputimagery of the sensor, would result in a uniform image when exposed tothose particular radiance sources.

However, since the response of each pixel is typically non-linear tosome degree, the true response of the array will depart from the linearmapping of NUC, resulting in spatial noise in the imagery, commonlyknown as residual fixed pattern noise, or FPN, or RFPN. This additionalnoise adds to the temporal and system noise of the sensor, reducing itsoverall sensitivity and detection capability. The further the radiancelevel the source is from the radiance levels used to calculate the NUCterms, the more FPN that is typically present in the imagery. As aresult, it is a common practice to use radiance levels that bracket therange of radiances expected from the scene to minimize the impact ofthis FPN.

In the visible spectrum, widely spaced radiance levels can beaccomplished through the use of a lamp source and a shutter, which canprovide both a sufficiently bright source and a very dark source tobracket the radiance levels of a scene. This is not, however, easilyaccomplished in the longwave infrared, or LWIR, spectrum, where theradiance sources are thermal in nature. Achieving a high radiance sourcecan be accomplished with a warm, high emissivity, blackbody target. Thehigh emissivity reduces any reflected sources from other targets andprovides higher radiance levels at lower temperatures. Achieving a lowradiance source, however, is more difficult. For example, the radianceoutput in the LWIR for a target with a temperature of 0° C. is only halfthat of a target with a temperature of 40° C. While objects in the scenemay be bounded by temperatures over this range, their emissivity canrange from very low to very high, resulting in a range of radiancevalues in the scene from equally very low to very high. To reduce theimpact of FNP, there is a need for low radiance sources, andunfortunately reducing the emissivity of a radiance target onlyincreases the amount of transmitted or reflected radiance from sourcesoutside of the target, resulting in inaccurate knowledge of the targetradiance as well as eliminating the benefit of the lower emissivity.Operating the radiance source at temperatures below 0° C. presents itsown problems in that they cannot be used in the presence of air due tocondensation and potential frost on the surface of the source thatcorrupts its radiance output.

There is therefore a need for a device to provide lower radiance sourcesfor non-uniformity correction than that which is currently available.

SUMMARY

The embodiments of the present teachings provide non-uniformitycorrection devices that are capable of providing low radiance levelsources. More specifically, one or more embodiments of the disclose anddescribe a first source of electromagnetic radiation, an opticalsubassembly having at least one optical element; the optical subassemblybeing configured to substantially receive a portion of theelectromagnetic radiation from said first source, a detector, anenvironmental device substantially capable of providing an operatingenvironment suitable for the detector, the environmental device beingsubstantially capable of receiving a portion of the electromagneticradiation from said optical subassembly, the detector beingsubstantially capable of receiving a portion of the electromagneticradiation transmitted by said environmental device, a second source ofelectromagnetic radiation, the second source being disposed within theoperating environment of said environmental device, and the detectorbeing substantially capable of receiving electromagnetic radiation fromthe second source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of an imaging optical system taken along theplane containing its optical axis;

FIG. 1B illustrates the dynamic range in radiance for two blackbodysources;

FIG. 2 is a schematic view of an embodiment of the present invention,taken along the plane containing its optical axis;

FIG. 3 is a schematic view of a further embodiment of the presentinvention, taken along the plane containing its optical axis;

FIG. 4A is a schematic view of a further embodiment of the presentinvention, taken along the plane containing its optical axis;

FIG. 4B is a schematic view of the embodiment of the present inventionof FIG. 4A, taken along the plane containing its optical axis;

FIG. 4C illustrates the dynamic range in radiance for the embodiment ofthe present invention of FIG. 4A;

FIGS. 5A and 5B are schematic views of a further embodiment of thepresent invention, taken along the plane containing its optical axis;

FIGS. 6A and 6B are schematic views of a further embodiment of thepresent invention, taken along the plane containing its optical axis;

FIG. 7A-7C are schematic views of a further embodiments of the presentinvention, taken along the plane containing its optical axis;

FIGS. 8A, 8B, and 8C are schematic views of a further embodiment of thepresent invention, taken along the plane containing its optical axis;

FIG. 8D illustrates the dynamic range and sampling in radiance for theembodiment of the present invention of FIGS. 8A, 8B, and 8C;

FIG. 9 is a schematic view of an optical pupil relay system taken alongthe plane containing its optical axis;

FIG. 10 is a schematic view of a further embodiment of the presentinvention, taken along the plane containing its optical axes;

FIGS. 11A, 11B, 11C and 11D are schematic views of a further embodimentof the present invention, taken along the plane containing its opticalaxes; and

FIGS. 12A, 12B, 12C and 12D are schematic views of a still furtherembodiment of the present invention, taken along its optical axis.

DETAILED DESCRIPTION

Reference is made to FIG. 1A, which is a schematic view of an opticalimaging system 100 taken along the plane containing its optical axis 10.In operation, electromagnetic radiation, typically in the ultraviolet,visible, and/or infrared bands, hereinafter referred to generally aslight, emitted or reflected by a given object, such as but not limitedto a blackbody radiator, hereinafter referred to generally as the source20, is incident onto an optical system 80. Light emitted by the sourceis incident onto an entrance pupil 30, which is capable of substantiallyreceiving a portion of the light from the source. The light is thenincident onto an imaging optical system 40, in this embodiment made upof, but not limited to, four refractive elements 42, 44, 46, and 48,which is capable of substantially receiving a portion of the light fromthe entrance pupil 30. The light is then incident upon an optical window50, which is capable of substantially receiving a portion of the lightfrom the imaging optical system 40. The light is then substantiallyfocused onto a focus position (hereinafter also referred to as an imageplane, which is typically planar, but without loss of generality mayalso be a curved or other non-planar surface) of a CCD array, CMOSimager, phosphorescent screen, photographic film, microbolometer array,or other means of detecting light energy, hereinafter referred togenerally as a detecting element 60. The detecting element 60 is locatedwithin a Dewar or other means of providing an operating environment,hereinafter referred to generally as a Dewar 70.

Reference is made to FIG. 1B which illustrates for the case of a longwave infrared imaging system the radiance of a typical blackbody sourceoperating at temperatures of 10 and 30° C. From this illustration, itcan be seen that this range of source temperatures provides only a smallrange of radiances for performing non-uniformity correction orradiometric calibration of the sensor.

Reference is made to FIG. 2, which is a schematic view of an embodimentof the present invention 200 taken along the plane containing itsoptical axis 210. In operation, a source element, such as but notlimited to an emissive plate or blackbody, hereinafter referred togenerally as a source element 220, is located within the environment ofthe Dewar 70 such that its temperature is substantially decreasedrelative to the temperature outside of the Dewar 70. The source elementis optically disposed in front of the detecting element 60, typically ina configurable manner by means of, but not limited to, a translational,rotational, or flip mechanism, such that light emitted by the source 220is incident onto the detecting element 60.

Reference is made to FIG. 3, which is a schematic view of anotherembodiment of the present invention 300 taken along the plane containingits optical axis 310. In operation, a reflective element, such as butnot limited to a mirror, hereinafter referred to generally as areflective source element 320, is located within the environment of theDewar 70 and optically disposed in front of the detecting element 60,typically in a configurable manner by means of, but not limited to, atranslational, rotational, or flip mechanism, or by electro-opticalmeans such as a switchable diffractive mirror or MEMS device, such thatlight emitted by cold objects located within the Dewar 70, including butnot limited to the detecting element 60 itself, is incident onto thereflecting element 320, which is capable of receiving a portion of thelight and reflecting it onto the detecting element 60.

Reference is made to FIG. 4A, which is a schematic view of a firstconfiguration of another embodiment of the present invention 400 takenalong the plane containing its optical axis 410. In operation, lightemitted by the source 20, is incident onto an entrance pupil 30, whichis capable of substantially receiving a portion of the light from thesource 20. The light is then incident onto an imaging optical system 40,in this embodiment made up of, but not limited to, four refractiveelements 42, 44, 46, and 48, which is capable of substantially receivinga portion of the light from the entrance pupil 30. The light is thenincident upon an optical window 50, which is capable of substantiallyreceiving a portion of the light from the imaging optical system 40. Thelight is then incident upon a transmitting optical element, such as butnot limited to a window, hereinafter referred to generally as atransmitting source element 420, which is located within the environmentof the Dewar 70, optically disposed in front of the detecting element60, typically in a configurable manner by means of, but not limited to,a translational, rotational, or flip mechanism, or by electro-opticalmeans such as a switchable diffractive window, and capable ofsubstantially receiving a portion of the light from the optical window50. The light is then substantially focused onto a detecting element 60,which is located within the Dewar 70 and capable of substantiallyreceiving a portion of the light transmitted by the optical element 420.

Reference is made to FIG. 4B, which is a schematic view of a secondconfiguration of the embodiment of the present invention 400 illustratedin FIG. 4A taken along the plane containing its optical axis 410. Inthis embodiment, the optical element 420 can be switched, closed,re-oriented, electrically converted, or otherwise modified to besubstantially opaque such that in this configuration light emitted bythe optical element 420 is incident onto the detecting element 60.

Reference is made to FIG. 4C which illustrates for the case theembodiment of the present invention 400 illustrated in FIGS. 4A and 4Bthe radiance seen by the detecting element 60 for the source 20operating at a temperature of 30° C. with the optical element 420operating in its transparent and opaque configurations. From thisillustration, it can be seen that the range of radiances for performingnon-uniformity correction or radiometric calibration of the sensor isgreatly increased.

Reference is made to FIG. 5A, which is a schematic view of anotherembodiment of the present invention 500 taken along the plane containingits optical axis 510. In operation, light emitted by cold objectslocated within the Dewar 70, including but not limited to the detectingelement 60 itself, is incident onto an optical window 50, which iscapable of substantially receiving a portion of the light from the coldobjects located within the Dewar 70. The light is then incident onto animaging optical system 40, in this embodiment made up of, but notlimited to, four refractive elements 42, 44, 46, and 48, which iscapable of substantially receiving a portion of the light from theoptical window 50. The light is then incident upon a reflecting element520, which in this embodiment is optically disposed to be substantiallyproximate to, but not limited to, an entrance pupil 30 of the imagingoptical system 40, and is capable of substantially receiving a portionof the light from the imaging optical system 40 and substantiallyreflecting the light.

Reference is made to FIG. 5B, which is a schematic view of the presentinvention 500 illustrated in FIG. 5A taken along the plane containingits optical axis 510. In continuance of its operation, light reflectedby the reflecting element 520 is incident onto the imaging opticalsystem 40, which is capable of substantially receiving a portion of thelight reflected from the reflecting element 520. The light is thenincident upon the optical window 50, which is capable of substantiallyreceiving a portion of the light from the imaging optical system 40. Thelight is then substantially focused onto the detecting element 60, whichis capable of substantially receiving a portion of the light transmittedby the optical window 50.

Reference is made to FIG. 6A, which is a schematic view of anotherembodiment of the present invention 600 taken along the plane containingits optical axis 610. In operation, light emitted by cold objectslocated within the Dewar 70, including but not limited to the detectingelement 60 itself, is incident onto an optical window 50, which iscapable of substantially receiving a portion of the light from the coldobjects located within the Dewar 70. The light is then incident onto animaging optical system 40, in this embodiment made up of, but notlimited to, four refractive elements 42, 44, 46, and 48, which iscapable of substantially receiving a portion of the light from theoptical window 50. The light is then incident upon a reflecting element620, which in this embodiment is optically disposed to be substantiallyproximate to, but not limited to, an entrance pupil 30 of the imagingoptical system 40, has substantially non-zero optical power, and iscapable of substantially receiving a portion of the light from theimaging optical system 40 and substantially reflecting the light.

Reference is made to FIG. 6B, which is a schematic view of the presentinvention 600 illustrated in FIG. 6A taken along the plane containingits optical axis 610. In continuance of its operation, light reflectedby the reflecting element 620 is incident onto the imaging opticalsystem 40, which is capable of substantially receiving a portion of thelight reflected from the reflecting element 620. The light is thenincident upon the optical window 50, which is capable of substantiallyreceiving a portion of the light from the imaging optical system 40. Thelight is then incident upon the detecting element 60, which is capableof substantially receiving a portion of the light transmitted by theoptical window 50. In this embodiment, the optical power of thereflecting element 620 is sufficient such the image of cold objectslocated within the Dewar 70 is substantially de-focused onto thedetecting element 60.

Reference is made to FIG. 7A, which is a schematic view of anotherembodiment of the present invention 700 taken along the plane containingits optical axis 710. In operation, light emitted by the source 20, isincident onto a first portion of an aperture 720, which in thisembodiment is optically disposed to be substantially proximate to, butnot limited to, an entrance pupil 30 of an imaging optical system 40,and is capable of substantially receiving a portion of the light fromthe source 20 and substantially transmitting the portion of light. Thelight is then incident onto an imaging optical system 40, in thisembodiment made up of, but not limited to, four refractive elements 42,44, 46, and 48, which is capable of substantially receiving a portion ofthe light from the aperture 720. The light is then incident upon anoptical window 50, which is capable of substantially receiving a portionof the light from the imaging optical system 40. The light is thensubstantially focused onto a detecting element 60, which is locatedwithin the Dewar 70 and capable of substantially receiving a portion ofthe light transmitted by the optical window 50.

Reference is made to FIG. 7B, which is a schematic view of theembodiment of the present invention 700 illustrated in FIG. 7A takenalong the plane containing its optical axis 710. In continuance of itsoperation, light emitted by cold objects located within the Dewar 70,including but not limited to the detecting element 60 itself, isincident onto the optical window 50, which is capable of substantiallyreceiving a portion of the light from the cold objects located withinthe Dewar 70. The light is then incident onto the imaging optical system40, which is capable of substantially receiving a portion of the lightfrom the optical window 50. The light is then incident upon a secondportion of the aperture 720, which is capable of substantially receivinga portion of the light from the imaging optical system 40 andsubstantially reflecting the portion of the light.

Reference is made to FIG. 7C, which is a schematic view of the presentinvention 700 illustrated in FIGS. 7A and 7B taken along the planecontaining its optical axis 710. In further continuance of itsoperation, light reflected by the second portion of the aperture 720 isincident onto the imaging optical system 40, which is capable ofsubstantially receiving a portion of the light reflected from thereflecting surface of the aperture 720. The light is then incident uponthe optical window 50, which is capable of substantially receiving aportion of the light from the imaging optical system 40. The light isthen substantially focused onto the detecting element 60, which iscapable of substantially receiving a portion of the light transmitted bythe optical window 50. The detecting element 60 substantially receives acombination of portions of light from the source 20 and from the coldobjects located within the Dewar 70.

Reference is made to FIG. 8A, which is a schematic view of a firstconfiguration of another embodiment of the present invention 800 takenalong the plane containing its optical axis 810. In operation, lightemitted by the source 20, is incident onto a first portion of anaperture 820, which in this embodiment is optically disposed to besubstantially proximate to, but not limited to, an entrance pupil 30 ofan imaging optical system 40, and is capable of substantially receivinga portion of the light from the source 20 and substantially transmittingthe portion of light. The light is then incident onto an imaging opticalsystem 40, in this embodiment made up of, but not limited to, fourrefractive elements 42, 44, 46, and 48, which is capable ofsubstantially receiving a portion of the light from the aperture 720.The light is then incident upon an optical window 50, which is capableof substantially receiving a portion of the light from the imagingoptical system 40. The light is then substantially focused onto adetecting element 60, which is located within the Dewar 70 and capableof substantially receiving a portion of the light transmitted by theoptical window 50.

Reference is made to FIG. 8B, which is a schematic view of a secondconfiguration of the embodiment of the present invention 800 illustratedin FIG. 8A taken along the plane containing its optical axis 810. Inthis configuration, its operation is substantially the same as theembodiment of the present invention 700 illustrated in FIGS. 7A, 7B, and7C, where a second portion of the aperture 820 in the embodiment 800 issubstantially the same as the aperture 720 in the embodiment 700.

Reference is made to FIG. 8C, which is a schematic view of a thirdconfiguration of another embodiment of the present invention 800 takenalong the plane containing its optical axis 810. In this configuration,its operation is substantially the same as the embodiment of the presentinvention 500 illustrated in FIGS. 5A and 5B, where a first portion ofthe aperture 820 in the embodiment 800 is substantially the same as thereflecting element 520 in the embodiment 500.

Reference is made to FIG. 8D which illustrates for the case theembodiment of the present invention 800 illustrated in FIGS. 8A, 8B, and8C the radiance seen by the detecting element 60 for the source 20operating at a temperature of 30° C. with the aperture 820 operating ineach of its configurations. From this illustration, it can be seen thatthe range of radiances for performing non-uniformity correction orradiometric calibration of the sensor is not only increased, but thatmultiple correction points spaced within that dynamic range can begenerated.

Reference is made to FIG. 9 which is a schematic view of an opticalpupil relay system 900 taken along the plane containing its optical axis910. In operation, light emitted by a source 920, which in thisembodiment is optically disposed to be substantially proximate to, butnot limited to, an entrance pupil 960 of an imaging optical system 940,is incident onto the imaging optical system 940, in this embodiment madeup of, but not limited to, four reflective elements 942, 944, 946, and948, which is capable of substantially receiving a portion of the lightfrom the source 920 and substantially imaging the entrance pupil 960onto an exit pupil 930.

Reference is made to FIG. 10, which is a schematic view of an opticalimaging system 1000 taken along the plane containing its optical axes 10and 910. In operation, light emitted by a source 920, which in thisembodiment is optically disposed to be substantially proximate to, butnot limited to, an entrance pupil 960 of an imaging optical system 940,is incident onto the imaging optical system 940, in this embodiment madeup of, but not limited to, four reflective elements 942, 944, 946, and948, which is capable of substantially receiving a portion of the lightfrom the source 920. The light is then incident upon a fold mirror 1040,which is capable of substantially receiving a portion of the light fromthe imaging optical system 940 and reflecting a portion of the light.The light is then incident upon an imaging optical system 80, which iscapable of substantially receiving a portion of the light from the foldmirror 1040 and substantially focusing the light onto a detectingelement 60, which is located within the Dewar 70.

Reference is made to FIG. 11A, which is a schematic view of a firstconfiguration of another embodiment of the present invention 1100 takenalong the plane containing its optical axes 10 and 910. In operation,light emitted by a source 920, which in this embodiment is opticallydisposed to be substantially proximate to, but not limited to, anentrance pupil 960 of an imaging optical system 940, is incident onto anoptical element 1120, which is optically disposed to substantiallyreceive a portion of the light from the source 920. The light is thenincident upon an imaging optical system 940, in this embodiment made upof, but not limited to, four reflective elements 942, 944, 946, and 948,which is capable of substantially receiving a portion of the light fromthe source 920. The light is then incident upon a fold mirror 1040,which is capable of substantially receiving a portion of the light fromthe imaging optical system 940 and reflecting a portion of the light.The light is then incident upon an imaging optical system 80, which iscapable of substantially receiving a portion of the light from the foldmirror 1040 and substantially focusing the light onto a detectingelement 60, which is located within the Dewar 70.

Reference is made to FIG. 11B, which is a schematic view of a secondconfiguration of the embodiment of the present invention 1100illustrated in FIG. 11A taken along the plane containing its opticalaxes 10 and 910. In operation, light emitted by cold objects locatedwithin the Dewar 70, including but not limited to the detecting element60 itself, is substantially transmitted by the imaging optical system 80onto the fold mirror 840, which is capable of substantially receiving aportion of the light from the imaging optical system 80 and the coldobjects located within the Dewar 70. The light is then incident onto theimaging optical system 940, which is capable of substantially receivinga portion of the light from the fold mirror 1040. The light is thenincident upon the optical element 1120, which in this embodiment can beswitched, closed, re-oriented, electrically converted, or otherwisemodified to be substantially reflective and is capable of substantiallyreceiving a portion of the light from the imaging optical system 940 andsubstantially reflecting the light.

Reference is made to FIG. 11C, which is a schematic view of the secondconfiguration of the embodiment of the present invention 1100illustrated in FIGS. 11A and 11B taken along the plane containing itsoptical axes 10 and 910. In continuance of its operation, lightreflected by the optical element 1120 is incident upon the imagingoptical system 940, which is capable of substantially receiving aportion of the light from the optical element 1120. The light is thenincident upon the fold mirror 1040, which is capable of substantiallyreceiving a portion of the light from the imaging optical system 940 andreflecting a portion of the light. The light is then incident upon theimaging optical system 80, which is capable of substantially receiving aportion of the light from the fold mirror 1040 and substantiallyfocusing the light onto the detecting element 60, which is locatedwithin the Dewar 70.

Reference is made to FIG. 11D, which is a schematic view of a thirdconfiguration of the embodiment of the present invention illustrated inFIGS. 11A, 11B, and 11C taken along the plane containing its opticalaxes 10 and 910. In this configuration, the fold mirror 1040 can bemoved, re-oriented, electrically displaced, or otherwise repositionedsuch that light from an external source (not shown) is incident upon theimaging optical system 80, which is capable of substantially receiving aportion of the light from the external source and substantially focusingthe light onto the detecting element 60, which is located within theDewar 70. Through these configurations, this embodiment of the presentinvention is capable of imaging external sources while also beingcapable of imaging internal sources as well as cold objects locatedwithin the Dewar to provide non-uniformity correction with an increaseddynamic range.

Reference is made to FIG. 12A, which is a schematic view of a firstconfiguration of another embodiment of the present invention 1200 takenalong the plane containing its optical axis 10. In operation, lightemitted by an external source (not shown) is incident onto a scanningmirror 1210, which is optically disposed to substantially receive aportion of the light from the external source. The light is thenincident upon an imaging optical system 1240, in this embodiment made upof, but not limited to, four reflective elements 1242, 1244, 1246, and1248, which is capable of substantially receiving a portion of the lightfrom the scanning mirror 1210. The light is then incident upon animaging optical system 80, which is capable of substantially receiving aportion of the light from the imaging optical system 1240 andsubstantially focusing the light onto a detecting element 60, which islocated within the Dewar 70.

Reference is made to FIG. 12B, which is a schematic view of a secondconfiguration of the embodiment of the present invention 1200illustrated in FIG. 12A taken along the plane containing its opticalaxis 10. In this embodiment, the scanning mirror 1210 can be moved,re-oriented, electrically displaced, or otherwise repositioned such thatlight emitted by a second source 20 is incident onto the scanning mirror1210, which is capable of substantially receiving a portion of the lightfrom the source 20. The light is then incident upon the imaging opticalsystem 1240, which is capable of substantially receiving a portion ofthe light from the scanning mirror 1210. The light is then incident uponthe imaging optical system 80, which is capable of substantiallyreceiving a portion of the light from the imaging optical system 1240and substantially focusing the light onto the detecting element 60,which is located within the Dewar 70.

Reference is made to FIG. 12C, which is a schematic view of a thirdconfiguration of the embodiment of the present invention 1200illustrated in FIGS. 12A and 12B taken along the plane containing itsoptical axis 10. In operation, light emitted by cold objects locatedwithin the Dewar 70, including but not limited to the detecting element60 itself, is substantially transmitted by the imaging optical system 80onto the imaging optical system 940, which is capable of substantiallyreceiving a portion of the light from the imaging optical system 80. Thelight is then incident upon the scanning mirror 1210, which is capableof substantially receiving a portion of the light from the imagingoptical system 1240 and in this embodiment can be can be moved,re-oriented, electrically displaced, or otherwise repositioned toreflect the light back towards imaging optical system 1240.

Reference is made to FIG. 12D, which is a schematic view of the thirdconfiguration of the embodiment of the present invention 1200illustrated in FIGS. 12A, 12B, and 12C taken along the plane containingits optical axis 10. In continuance of its operation, light reflected bythe scanning mirror 1210 is incident upon the imaging optical system1240, which is capable of substantially receiving a portion of the lightfrom the scanning mirror 1210. The light is then incident upon theimaging optical system 80, which is capable of substantially receiving aportion of the light from the imaging optical system 1240 andsubstantially focusing the light onto the detecting element 60, which islocated within the Dewar 70. Through these configurations, thisembodiment of the present invention is capable of imaging externalsources while also being capable of imaging internal sources as well ascold objects located within the Dewar to provide non-uniformitycorrection with an increased dynamic range.

Although the invention has been described with respect to variousembodiments, it should be realized this invention is also capable of awide variety of further and other embodiments within the spirit andscope of the invention. For example, any number of optical elements,reflective or refractive, can be used in the embodiments of the presentinvention, and any aspects of the embodiments of the present invention,including but not limited to those shown, can be used in combinationwith one another as still further embodiments, such that each portion ofthe object can be imaged by any method such as but not limited to thoseshown in the embodiments of the present invention. Still further,although the embodiments of the optical systems of the present inventionhave been shown a limited number of configurations, it should berealized that this invention can include any number of configurations.

What is claimed is:
 1. An optical imaging system comprising: a detector;an environmental device capable of providing an operating environmentsuitable for said detector; said environmental device being configuredto receive a portion of electromagnetic radiation from said detector; anoptical subassembly having at least one optical element; said opticalsubassembly being configured to receive a portion of the electromagneticradiation from said environmental device; a source of electromagneticradiation; a configurable element; said configurable element beingoptically disposed between said source and said optical subassembly;said configurable element being configurable such that, in a firstconfiguration, said configurable element is configured to reflect aportion of the electromagnetic radiation from said optical subassembly,and, in a second configuration, said configurable element is configuredto transmit a portion of the electromagnetic radiation from said source;said optical subassembly being configured to receive a portion of theelectromagnetic radiation reflected by said configurable element in saidfirst configuration; said optical subassembly being configured toreceive a portion of the electromagnetic radiation transmitted by saidconfigurable element in said second configuration; said environmentaldevice being configured to receive a portion of the electromagneticradiation from said optical subassembly; and said detector beingconfigured to receive a portion of the electromagnetic radiationtransmitted by said environmental device.
 2. The optical imaging systemof claim 1 wherein said at least one optical element is refractive. 3.The optical imaging system of claim 1 wherein said at least one opticalelement is reflective.
 4. The optical imaging system of claim 1 whereinsaid configurable element has no optical power.
 5. The optical imagingsystem of claim 1 wherein said configurable element has optical power.6. The optical imaging system of claim 1, wherein said configurableelement is configured to have a plurality of configurations, such that,in a third configuration in said plurality of configurations, saidconfigurable element is partially reflective or partially transmissiveto electromagnetic radiation.
 7. An optical imaging system comprising: adetector; an environmental device configured to provide an operatingenvironment suitable for said detector; said environmental device beingconfigured to receive a portion of electromagnetic radiation from saiddetector; an optical subassembly having at least one optical element;said optical subassembly being configured to receive a portion of theelectromagnetic radiation from said environmental device; a configurableredirecting element; said configurable redirecting element beingconfigured to redirect a portion of the electromagnetic radiation fromsaid optical subassembly back to said optical subassembly when saidconfigurable redirecting element is in a first configuration; a sourceof electromagnetic radiation; said configurable redirecting element alsobeing configured to redirect a portion of electromagnetic radiation fromsaid source to said optical subassembly when said configurableredirecting element is in a second configuration; said opticalsubassembly being configured to receive a portion of the electromagneticradiation redirected by said configurable redirecting element; saidenvironmental device being configured to receive a portion of theelectromagnetic radiation from said optical subassembly; and saiddetector being configured to receive a portion of the electromagneticradiation transmitted by said environmental device.
 8. The opticalimaging system of claim 7 wherein said at least one optical element isrefractive.
 9. The optical imaging system of claim 7 wherein said atleast one optical element is reflective.
 10. The optical imaging systemof claim 7 wherein said configurable redirecting element is reflective.11. The optical imaging system of claim 10 wherein said configurableredirecting element is a scanning mirror.
 12. An optical imaging systemcomprising: a detector; an environmental device configured to provide anoperating environment suitable for said detector; said environmentaldevice being configured to receive a portion of electromagneticradiation from said detector; an optical subassembly having at least oneoptical element; said optical subassembly being configured to receive aportion of the electromagnetic radiation from said environmental device;a configurable redirecting element; said configurable redirectingelement being configured to have a plurality of configurations; saidconfigurable redirecting element being configured to redirect a portionof the electromagnetic radiation from said optical subassembly back tosaid optical subassembly when said configurable redirecting element isin a first configuration; a plurality of sources of electromagneticradiation; said configurable redirecting element also being configuredto redirect a portion of electromagnetic radiation from at least onesource of electromagnetic radiation in said plurality of sources ofelectromagnetic radiation to said optical subassembly when saidconfigurable redirecting element is in at least one configuration ofsaid plurality of configurations; said optical subassembly beingconfigured to receive a portion of the electromagnetic radiationredirected by said configurable redirecting element; said environmentaldevice being configured to receive a portion of the electromagneticradiation from said optical subassembly; and said detector beingconfigured to receive a portion of the electromagnetic radiationtransmitted by said environmental device.
 13. The optical imaging systemof claim 12 wherein said at least one optical element is refractive. 14.The optical imaging system of claim 12 wherein said at least one opticalelement is reflective.
 15. The optical imaging system of claim 12wherein said configurable redirecting element is reflective.
 16. Theoptical imaging system of claim 15 wherein said configurable redirectingelement is a scanning mirror.
 17. The optical imaging system of claim 12wherein said plurality of configurations comprises a firstconfiguration, a second configuration, and a third configuration; saidplurality of sources of electromagnetic radiation comprises a firstsource of electromagnetic radiation and a second source ofelectromagnetic radiation; said configurable redirecting element beingconfigured to redirect a portion of the electromagnetic radiation fromsaid optical subassembly back to said optical subassembly when saidconfigurable redirecting element is said first configuration; saidconfigurable redirecting element also being configured to redirect aportion of electromagnetic radiation from said first source to saidoptical subassembly when said configurable redirecting element is insaid second configuration; and said configurable redirecting elementalso being configured to redirect a portion of electromagnetic radiationfrom said second source to said optical subassembly when saidconfigurable redirecting element is in said third configuration.